Stripping cathodes of electrodeposits



June 18, 1963 c. L. SCHEER 3,

STRIPPING CATHODES OF ELECTRODEPOSITS Filed Jan. 5. 1961 2 Sheets-Sheet 1 FIG. I

ENTOR.

C HARLES L. SCHEER m MMMEJ' ATTORNEYS V June 18, 1963 c. SCHEER STRIPPING CATHODES OF ELECTRODEPOSITS 2 Sheets-Sheet 2 Filed Jan. 5, 1961 R T E 8 RH E 06 N TS R L M0 E T VB T m m mm M M 0 PM m oI 3,994,437 STRKPPING CATHODE F ELECTRQDEPOSITS Charles Louis Scheer, Havertown, Pa, assignor to Foote Mineral (Tompany, Philadelphia, Pa, a corporation of Pennsylvania Filed inn. 5, 1961, Ser. No. 89,958 8 Claims. (Cl. 134l6) This invention relates to the stripping of electrolytically deposited material from the surface of cathodes .and, more particularly, to a novel method and apparatus for rapidly separating a brittle electrolytic metallic deposit from a flexible cathode sheet by subjecting the sheet to vigorous vibration. This application is a continuation-inpart of my co-pending application entitled Stripping Cathodes of Electrodeposits, Serial No. 721,570, filed March 14, 1958, which has become abandoned.

The method and apparatus are particularly adapted to stripping metallic manganese from the cathode sheets on which it is deposited in the electrolytic process for producing manganese metal. The cathodes employed in this process are substantially rectangular sheets of stainless steel or other metal. Since the manganese metal electrolytically deposited on them is quite brittle, it is common practice to strip the manganese from the sheets by manually flexing each sheet. As a result of such flexing the manganese breaks off in the form of a multitude of chips. This procedure, however, requires that personnel be assigned exclusively to the specific task of stripping the sheets. Moreover, it is not a very effective procedure for removing manganese from the lower corners of the sheet where the deposit has grown around the edges, .and as a result of such manual stripping operation the cathode sheets are usually deformed with bends especially at the lower corners.

Another stripping procedure is to suspend the cathode and strike the deposit repeatedly with a mallet or other instrument. Such treatment is injurious to the cathode, and is no more effective than flexing to remove the deposit at the corners of the sheet. Attempts have also been made to strip the deposit by heating the cathode with infra-red lamps. The differential in thermal expansion between the cathode and the deposit is then relied on to cause the deposit to break off. This scheme, however, has not proved practical.

It is a major purpose of this invention to provide a novel method for removing brittle electrolytically deposited manganese metal and other materials from cathode sheets which eliminates the manual flexing involved in heretofore conventional stripping methods. Furthermore, the invention provides novel apparatus by which the new method is efficiently carried out, thereby eliminating the need for the specialized personnel now assigned to the task of stripping the cathode sheets. The electrodeposit is rapidly and substantially completely removed from virtually the entire sheet without severely bending or deforming the sheet and without manual flexing or hammering.

in carrying out the new stripping method, a traveling fiexure wave is imparted to a cathode sheet over substantially its entire area by vibrating one end of the sheet through a substantially straight-line path of travel which at all points is substantially normal to the plane of the undistorted sheet. These vibrations preferably are of a frequency exceeding 19 cycles per second through an amplitude sufiicient to cause the brittle electrolytic deposit to separate rapidly and substantially completely from the entire area of the cathode sheet. The apparatus provided by the invention to carry out this novel method, comprises releasable vise jaws for firmly gripping one end of the cathode sheet. A vibrator is connected to the vise jaws. The vibrator is capable of imparting vibraatent ice tions through a straight-line path of travel in a horizontal plane and at a frequency and through an amplitude sufficient to cause the brittle electrolytic deposit to separate substantially completely from the entire area of the cathode sheet. Means are also included for preventing rotation of said jaws during motion thereof through the straight-line path of travel.

For maximum stripping effectiveness the vibratory force should be directed back and forth in a direction normal to the plane of the cathode sheet. Cam driven vibrators arranged to impart vibrations which have one component of force directed parallel to the plane of the cathode, such as unloading or packing vibrators which accelerate one edge of the cathode through a circular path in a plane normal to the cathode sheet, are relatively less effective than vibrators arranged to accelerate one edge of the cathode through a linear path normal to the cathode sheet.

Vibration of the cathode back .and forth in a direction normal to its plane produces a wave having a substantially shorter radius of curvature than is generally developed by flexing and insures that the entire area of the cathode is subjected to motion through this small radius of curvature. As a result a substantially greater shearing action is exerted at the interface of the cathode and the electrodeposit, and is applied over the entire area of that interface. By creating a relatively low frequency traveling wave (advantageously of 30 to cycles per second) of fairly high amplitude in the cathode, complete separation of the deposit from the cathode is quickly achieved. As the wave travels along the cathode, the point of maximum shear force travels with it, thus in suring that this maximum force is applied uniformly over the entire area of the cathode. It is of course important that the energy of the wave be quite fully absorbed in the sheet in order to achieve good stripping efficiency, and this condition is best met by restraining the edge of the cathode, opposite the edge to which the vibratory force is applied, from substantially all motion.

Pereferred embodiments of both the contemplated method and the apparatus are described below with reference to the accompanying drawings, wherein FIG. 1 is a schematic elevation of one embodiment of the new stripping apparatus;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a schematic elevation of another embodiment of the new stripping apparatus; and

FIG. 4 is an elevation partly broken away showing a cathode sheet and carriage means for carrying the sheet into position within the stripping apparatus.

In the first embodiment of the apparatus, as illustrated in FIGS. 1, 2 and 4, a flexible rectangular stainless steel cathode sheet 1E1 of the type used in the electrolytic recovery of manganese is equipped with a rigid supporting and contact bar 11 welded or otherwise securely fastened to its upper edge. The extremities of the supporting bar 11 extend beyond each longitudinal edge of the sheet and may have holes 11 (FIG. 4) formed therein to provide means by which the cathode sheet may be suspended on a conveyor. Prior to being stripped in the manner described hereinbelow, each cathode sheet 10 is covered on both sides with a continuous brittle electrodeposit of manganese metal in a uniform layer about inch or more thick.

As seen in FIGS. 1 and 4, and a conveyor is provided by which a succession of the cathode sheets 10 may be carried to and from the stations at which the manganese deposit is stripped therefrom. The conveyor includes overhead rails 12 and a carriage 13 supported thereon by pairs of rotatably mounted rollers 14 and 15. Supporting rods or cables 16 depend from opposite ends of a carriage 13, and have hooks 1% attached to their lower extremities. The actual length of the rods 16 for this embodiment of the apparatus is indicated in FIG. 1 only since in FIG. 4 there central portion is broken away.

The rods'dfi are spaced apart on the carriage .13 so that the holes 111' at opposite extremities of the supportingbar 1-1 on each cathode sheet It} can accommodate the hooks 18 and 19. in this manner, the cathode sheet is suspended from the carriage l3 and can be car-- ried along beneath the rails 12. Although not shown in the drawings since it forms no part of the invention, some suitable type of driving means, such as an endless chain running over a driving sprocket, may be employed in association with the conveyor to move the carriage 13 automatically along the rails.

An enclosure 23 is constructed around and beneath the overhead rails 12 in the path of the cathode sheets lid conveyed along the rails by a carriage 13. Cut-out portions 24 and entry and exit slots 25 are provided in the side walls of the enclosure 23- to permit the carriages 13 and any cathode sheets suspended therefrom to pass into and out of the enclosure as they are moved along the rails 12. Since the separation of the manganese deposit from the cathode sheets is effected within the enclosure 23:, a hopper 26 is provided in the floor of the enclosure to catch the manganese as it is removed; and an endless belt or other suitable conveyor means may, if desired, be provided beneath such a hopper to carry the manganese chips away from the enclosure 23 to a storage area or to weighing and packaging apparatus.

Mounted on a suitable foundationZd adjacent the enclosure 23 is a vibrator 29. This vibrator may be either an electromagnetic or mechanical type having a vibrator element 30 in which may be induced vibrations above 10 cycles per second, and advantageously from 30 to 150 cycles per second, at an amplitude of at least or /8 inch, and advantageously /2 inch or more. Preferably the vibrator 29 is one of the commercially available models having an output thrust of 600-800 pounds at a frequency of from 40 to 70 cycles per second and an amplitude of about /2 inch. These operating characteristics may be varied, however, to adapt the unit to different stripping requirements.

Within the enclosure 23 are provided means to restrain movement of the entire lower edge of any cathode sheet 10 carried into the enclosure by the carriage 13, though such restraining means is not always necessary and can be dispensed with in many instances. A restraining slot 3'5 defined by a pair of angle irons 36 is positioned in the lower portion of the enclosure 23 adjacent the bottom of the entry and exit slots 25. When a cathode sheet 10 is carried into the enclosure 23 by the carriage 13, the lower edge of the sheet enters the restraining slot 35 and is prevented from moving laterally by the angle irons 36. As seen in FIG. 2, the angle irons at the entry end of the slot 35 are flared outwardly to guide the lower edge of the sheet 10 into position.

Means are also included within the enclosure 23 to permit the central portion of the supporting bar 11 of the cathode 10 to be seized over a distance equal to the greater part of its length. Releasable vise jaws 33 associated with a double-acting compressed air cylinder 3d are provided. The jaws 38 and cylinder 39 are mounted on a frame 40 which is pivotally attached to the end of the ivibrator element 30 at an elbow joint 41. The joint 41 permits the vise jaws 38 and the cylinder 39 to be swung upwardly to the position shown by the dotted lines in FIG. 1 so that a carriage 13 with a cathode sheet 10 suspended therefrom may be moved into and out of the enclosure 23. To swing the cylinder upwardly in this manner, a small winch 42 is mounted on top of the enclosure 23 with a flexible cable 43 running over'a pulley 44 and downwardly through an aperture in the enclosure 23 to the outer end of the cylinder 39. By activating the winch 42 and drawing in the line 43, the vise apparatus 4- may be quickly drawn up to the position shown by dotted lines in FIG. 1; and by reversing the winch vise apparatus may be equally quickly lowered to position shown in solid lines.

In the operation or the apparatus illustrated in FIG. 1, the cylinder 39 and the vise jaws 38 on the frame 443 are lifted to the position shown in the dotted lines to permit a cathode sheet 1t} carrying a maganese deposit to be moved into the enclosure 23 suspended from the carriage i3. When the carriage 13 is directly opposite the vibrator element St, the carriage is stopped. The lower edge of the cathode sheet 10 is received in the restraining slot 35' when the carriage 13 is in this position. Then the vise jaws are swung down over the supporting bar 11 by paying out on the cable 43 from the winch 4-2, and the compressed air cylinder 39 is operated to close the jaws 35 and cause it to seize the central portion of the supporting bar 11 over a distance equal to the greater part of its length.

The vibrator 29 is then activated, preferably at a fre quency of about 60 cycles per second through an amplitude of approximately /2 inch to impart vigorous vibrations to the cathode sheet 10. Such vibration suffices to cause the brittle electrolytic manganese to separate substantially completely from the entire area of the cathode sheet, even the area in the restraining slot 35 and even at the lower corners of the sheet. As the manganese falls in chip form from the cathode sheet it enters the hopper 26 and is carried therethrough to storage or to packaging apparatus. After all of the manganese has been removed from the cathode sheet 10 in this manner (the time required is only a few seconds), the cylinder 39 is operated to release the vise jaws from the supporting bar 11, and the vise apparatus then is lifted clear of the sheet 10 by the winch 42. The stripped cathode sheet it) is then carried out of the enclosure 23 on the carriage d3 through the exit slot 25 in the wall of the enclosure.

Referring now to the embodiment of the apparatus illustrated in FIG. 2, elements which are identical to those in the embodiment of FIG. 1 are denoted by the same reference numerals. A cathode sheet 10, equipped with a contact and supporting bar 11, is suspended from a conveyor comprising a carriage 50 adapted to be supported upon overhead rails 51 by means of two pairs of rotatably mounted rollers 52., 52. From each end of the carriage 40 depends a supporting rod or cable 53 having a hook 54 attached to its lower extremity. These hooks are adapted to be received in the holes 11 in the supporting bar 11 of a cathode sheet 10. The construction is similar to that of the conveyor means illustrated in FIG. 4, except that the supporting rods 53 may be considerably shorter than the supporting rods 16.

An enclosure 55 is positioned about the overhead rails 5-1 and includes cut-out portions 56 and entry and exit slots 57 which permits the cathode sheet 10 to be carried into and out of the enclosure by the conveyor means. A hopper 2.6 is again included in the floor of the enclosure as in the previous embodiment and the vibrator 29 with its vibrator element 30 is mounted adjacent the enclosure 55 on a foundation 56.

In this second embodiment, the vibrator Z9 is adapted to transmit vibrations to the cathode sheet 10 through its lower edge, rather than through the supporting bar 1-1 on its upper edge as described with reference to FIG. 1. Releasable vise jaws 60 are affixed to a frame 61 which is rigidly attached to the vibrator element 30 of the vibrator 29. A first double-acting compressed air cylinder 62 is also affixed to the frame 61 to open and close the vise jaws 60 as desired. The jaws 6d are positioned directly beneath the conveyor rails 51 at the same elevation as the lower edge of the cathode sheet 10, so that the lower edge of the sheet readily enters the vise jaws 66 when the carriage 50 is moved into'the enclosure. Similar to the design shown in FIG. 3, the entry end of the vise jaws may be flared outwardly to aid in guiding the lower edge of the the the the sheet into position. The outer end of the cylinder 62 is supported by an arm 63, depending from a frame 64,

which does not impede vibration of the vise jaws 60.

Also mounted on the frame 64 is a second compressed air cylinder 66 which is adapted to urge a movable vise jaw 67 against an opposed stationary vise jaw 68 extending from the opposite wall of the enclosure 55. The movable and stationary vise jaws 67 and 68 are located substantially directly beneath the conveyor rails 51 in line with the entry and exit slots 57 in the enclosure 55, and are at an elevation such that they are adapted to engage the supporting bar 11 on any cathode sheet 10 carried into the enclosure by a carriage 50. The movable and stationary vise jaws 67 and 68 are also adapted to seize the supporting bar 11 at its central portion along a substantial part of its entire length.

In operation of the apparatus of FIG. 2, a cathode sheet 10 with its covering of electrolytically deposited manganese is carried into the enclosure 55 through the entry slot 57 and is halted opposite the vibrator element 30. The supporting bar 11 of the sheet 19 is then between the movable and stationary vise jaws 67 and 6S, and substantially the entire lower edge of the sheet 10 is between the vise jaws 60. The first compressed air cylinder 62 is operated to cause the vise jaws 60 to firmly seize the lower edge of the sheet 14 along substantially its entire length, and the second compressed air cylinder 66 is operated to seize the central portion of the supporting bar 11 firmly between the movable and stationary vise jaws 67 and 68. The vibrator 29 is then activated to impart vigorous vibrations to the seized lower edge of the sheet it) :at a frequency of approximately 60 cycles per second through an amplitude of approximately /2 inch. The electrolytic manganese deposit on the surface of the sheet 16 is thereby quickly and substantially completely separated from the sheet 10 and falls in chip form into the hopper 26; and even the portion of the deposit gripped between the lower vise jaws 6t) separates substantially completely from the sheet and falls into the hopper when these jaws are released. As with the apparatus of FIG. 1, only a few seconds is required to fully strip the cathode of its electrodeposit.

It will be noted that in both of the embodiments de scribed above, the vibrators are arranged to impart motion to the cathode back and forth linearly in a direction normal to the plane of the cathode. Thus substantially the entire energy input serves to produce a wave motion which travels along the sheet from edge to edge. This wave motion subjects all parts of the cathode uniformly to movement through a radius of curvature which is small enough to exert a high shearing force at the interface of the cathode sheet and the manganese electrodeposit. The result is that the bond between the electro deposited layer and the cathode sheet is quickly and completely broken over the entire area of the cathode. Because of the high shearing force applied to the interface, it is possible to strip deposits quickly and completely even though the bond to the cathode is strong. A consequent advantage of the invention is that it greatly reduces the degree of control that need be exercised over the condition of the cathode surface to insure easy stripping of the electrodeposit. Cathodes having surfaces which would be unacceptable if the electrodeposit had to be stripped by manual flexing (because then only incomplete stripping would be possible), can 'be used successfully and stripped completely of the electrodeposit when the stripping method and apparatus of this invention are employed.

While the invention has been particularly described with reference to stripping electrolytic manganese deposits, it is evident that it can be applied successfully to stripping deposits of other materials, especially deposits of a brittle nature, such as brittle copper deposim, lead peroxide deposits, etc, from flexible sheet electrodes.

I claim:

1. The method of stripping a brittle electrolytic deposit from a flexible cathode sheet which comprises substantially completely restraining one end of said cathode sheet from movement, and imparting a traveling flexure wave to said sheet by vigorously vibrating the opposite end through a substantially straight-line path of travel which at all points is substantially normal to the plane of the undistorted sheet, whereby the brittle electrolytic deposit is rapidly and substantially completely separated from the entire area of the cathode sheet.

2. The method of stripping a brittle electrolytic deposit from a flexible cathode sheet which comprises substantially completely restraining one end of said cathode sheet from movement, and imparting a traveling flexure wave to said sheet over substantially its entire area by vibrating the opposite end of said sheet through a substantially straight-line path of travel which at all points is substantially normal to the plane of the undistorted sheet at a frequency of from 30 to cycles per second through an amplitude suflicient to cause the brittle electrolytic deposit to separate rapidly and substantially completely from the entire surface area of the cathode sheet.

3. The method of stripping a brittle electrolytic deposit of metallic manganese from a flexible. substantially rectangular cathode sheet which comprises substantially completely restraining one end of said sheet from movement, and imparting a traveling flexure wave to said sheet over substantially its entire area by vibrating the opposite end of said sheet through a substantially strightline path of travel which at all points is substantially normal to the plane of the undistorted sheet at a frequency of from 30 to 150 cycles per second through an ampliutde suflicient to cause the brittle manganese deposit to separate substantially completely from the entire surface area of the cathode sheet.

4. The method of stripping a brittle electrolytic deposit of metallic manganese from a cathode comprising a thin metallic sheet having a relatively rigid supporting bar secured to and extending across its upper edge, which comprises seizing the central portion of the cathode supporting bar over a substantial part of its length, and imparting a traveling flexure wave to said sheet over substantially its entire area by vigorously vibrating the seized bar through a substantially straight-line path of travel which at all points is substantially normal to the plane of the undistorted sheet while restraining the opposite end of the cathode from substantially all movement, whereby the metallic manganese deposit is rapidly and substantially completely dislodged from the entire area of the cathode sheet.

5. Apparatus for stripping a brittle electrolytic deposit from a flexible substantially rectangular cathode sheet comprising means for suspending said sheet in a substantially vertical plane, restraining means for engaging one end of said sheet and preventing substantially all movement thereof, releasable vise jaws for firmly gripping the opposite end of said cathode sheet, a vibrator connected to said vise jaws for imparting vigorous vibrations thereto through a straight-line path of travel in a horizontal plane, and means preventing rotation of said jaws during motion thereof through said straight-line path of travel.

6. Apparatus for stripping a brittle electrolytic deposit from a flexible substantially rectangular cathode sheet having a relatively rigid supporting bar secured to and extending across its upper edge, comprising hanger means for engaging said supporting bar and suspending said sheet in a substantially vertical plane, releasable vise jaws for seizing the central portion of the cathode supporting bar over a distance equal to the greater part of its length, a vibrator connected to said vise jaws for imparting vigorous vibrations thereto through a straight-line path of travel in a horizontal plane, and means preventing rotation of said jaws during motion thereof through said straight-line path of travel.

7. Apparatus for stripping a brittle electrolytic deposit from a flexible substantially rectangular cathode sheet having a relatively rigid supporting bar secured to and extending across its upper edge, comprising a conveyor for suspending and carrying said sheet by said supporting bar in a substantially vertical plane, restraining members defining a slot adapted to receive the lower edge of said cathode sheet and preventing substantially all movement thereof, said restraining members being positioned relative to said conveyor to permit said sheet to be carried by said conveyor into and out of said slot, releasable vise jaws for seizing the central portion of the cathode supporting bar over a substantial part of its length, a vibrator connected to said vise jaws for imparting vigorous vibrations to said cathode sheet when the lower edge of said sheet is engaged by said restraining slot and the cathode supporting bar is gripped in said jaws through a straight-line path of travel in a horizontal plane, and means preventing rotation of said jaws during motion thereof through said straight-line path of travel.

8. Apparatus for stripping a brittle electrolytic deposit from a flexible substantially rectangular cathode sheet having a relatively rigid supporting bar secured to and extending across its upper edge, comprising a conveyor for suspending and carrying said sheet by said supporting bar, in a substantially vertical plane, a set of releasable vise jaws adapted to engage the cathode supporting bar, said vise jaws being positioned relative to conveyor to permit said sheet to be carried by said conveyor into and out of said jaws when the jaws are released, a vibrator connected to said vise jaws for imparting vigorous vibrations thereto when the cathode supporting bar is gripped by said jaws through a straight-line path of travel in a horizontal plane, and means preventing rotation of said jaws during motion thereof through said straight-line path of travel.

References Cited in the file of this patent UNITED STATES PATENTS 1,077,867 Becker Nov. 4, 1913 1,842,232 Baker Jan. 19, 1932 2,123,464 Engelman July 12, 1938 2,591,444 L'azan Apr. 1, 1952 2,744,860 Rines May 8, 1956 

1. THE METHOD OF STRIPPING A BRITTLE ELECTROLYTIC DEPOSIT FROM A FLEXIBLE CATHODE SHEET WHICH COMPRISES SUBSTANTIALLY COMPLETELY RESTRAINING ONE END OF SAID CATHODE SHEET FROM MOVEMENT, AND IMPARTING A TRAVELING FLEXURE WAVE TO SAID SHEET BY VIGOROUSLY VIBRATING THE OPPOSITE END THROUGH A SUBSTANTIALLY STRAIGHT-LINE PATH OF TRAVEL WHICH AT ALL POINTS IS SUBSTANTIALLY NORMAL TO THE PLANE OF THE UNDISTORTED SHEET, WHEREBY THE BRITTLE ELECTROLYTIC DEPOSIT IS 